Bostik T630 AIRSEAL SEALING TAPE 3D Compressed Multi-Functional Window Surrounding Sealing Foamtape is unrolled from the spool directly onto the cleaned PVC-U window frame perimeter after the four-head welder and CNC corner cleaner have removed weld flash and extrusion burr. The tape is positioned with the release liner facing outward. Application at substrate temperatures between +5 °C and +40 °C avoids condensation-induced loss in initial tack. The PVC-U surface is wiped with a lint-free cloth dampened with an aqueous alcohol solution to remove wax, extrusion lubricant, and corner cleaning residue. A pressure roller with Shore A 60–70 durometer is run along the tape at a constant feed rate. Edge pressure is concentrated at the outer perimeter. On high-speed applicator lines, a known failure mode is corner lift when the release liner is peeled under tension below +10 °C. The release liner is left intact until the frame is packed for site installation. Compression set after long-term storage on the frame is a further failure mode. When the tape remains factory-compressed in packaging for more than 8 weeks at ambient temperatures above 25 °C, recovery before installation may be reduced. Compression set is measured according to ISO 1856-2018. Published data for this specific storage configuration is limited. The tape is not re-rolled after application. Terminal window units are packed vertically to avoid localized foam crushing. The compressed thickness at the rough opening is determined by the frame fixing sequence and shim placement. When a 10 mm wide tape is compressed to 3 mm in the rough opening, the resulting 70% compression ratio places the foam in a high-density state. This state is appropriate only where rough opening tolerance is held to ±2 mm. Exceeding this tolerance produces void formation at low spots and over-compression at high spots. On production lines with digital frame routers, the tape is applied after hardware routing but before glass glazing. The finished casement or tilt-and-turn sash is then installed into the prepared building opening. The tape contributes to the air barrier continuity demanded by ASTM E2112-19. It does not replace structural shims or anchor fasteners. Air leakage at the junction is assessed under ASTM E283-04. Water penetration resistance is assessed under ASTM E331-00. Joint movement capability is qualified through cyclical loading procedures referenced in EN 1027-2016 and EN 1026-2016. The installer must verify compatibility with the PVC-U grade. Some extruded profiles contain high levels of external lubricant. These lubricants reduce peel adhesion. Cleaning alone may not restore full tack. An acrylic dispersion primer may be required. The adhesive side is sensitive to frost. Application below +5 °C without pre-warming the frame is not recommended. The compressed cellular structure resists liquid water migration. The outer cell surface allows controlled vapour transmission. The precise permeability depends on joint compression and is measured under EN ISO 12572-2016. High compression reduces vapour transmission. Joint design must account for this. The tape is not a structural connection. Fastener torque is limited by the PVC-U profile. Over-torquing deforms the profile and alters tape compression. The tape is not intended for continuous immersion. At sill locations, water must drain outward. The tape is cut flush with sill drainage slots. The rough opening must be clean, dry, and frost-free. The window frame is set level and square before full compression. Shims are located at load points. The tape is compressed by pulling the frame into the opening with fixing screws. After installation, the tape expands to fill residual gaps. The maximum gap to be filled must not exceed the recovery limit declared by the manufacturer. Field gaps larger than this require a backer rod and an additional sealant. The terminal window unit is then glazed and commissioned.

What Limits Cyclic Joint Movement in Aluminium Curtain Wall Mullion Interfaces?

Aluminium mullion systems impose a different load case from punched window openings. The mullion expands and contracts with the external surface temperature. The linear thermal expansion coefficient of aluminium is 23.1 × 10⁻⁶ K⁻¹. A 3 m mullion subjected to a 60 K thermal shift approaches 4.2 mm length change. The tape is installed in the mullion rebate or against the rough opening boundary. It must absorb differential movement without losing interface contact. Cyclic wind load reversal is a further degradation mechanism. Negative pressure on the spandrel area pulls the frame away from the rough opening. Positive pressure pushes the frame inward. The tape experiences a repeated strain cycle. If the compressed foam is forced beyond its recovery limit during the negative-pressure half-cycle, a permanent set develops. The joint opens on the next thermal contraction. This produces a leakage path at the mullion head and sill. Curtain wall mock-up testing under ASTM E283-04 and ASTM E330/E330M-14 should include the tape in the same compressed state as the final installation. The use of a 5–8 mm nominal joint width is common in aluminium unitised systems. The tape must not be compressed below 30% of its original thickness. Lower compression reduces recovery force and allows capillary water entry at the interface. Higher compression above 70% risks cohesive foam splitting after repeated thermal cycles. The aluminium frame surface is prepared by removing cutting oil and aluminium swarf. A solvent wipe with a ketone or alcohol is used only where the surface is anodised or powder-coated. Bare mill-finish aluminium may carry residual rolling oils. In such cases, a primer is applied to the bonding face. The tape is cut with a guillotine knife, not torn. The corners are overlapped or butted. At the intersection of mullion and transom, the tape is discontinuous until the surrounding gasket and weather seal are installed. The tape is not expected to act as a structural sealant. The structural silicone joint is separate. The final unitised panel is craned into place and anchored to the floor slab. The rough opening bracket locations are fixed. Any misalignment of the panel creates non-uniform tape compression. The perimeter tape is inspected before the interior trim is installed. A feeler gauge of 0.2 mm is used to detect open voids. Published data for Bostik T630 under this specific cyclic mullion configuration is limited. Project-specific mock-up testing is required.

Timber window and door retrofit installations expose the tape to a rough opening that may vary from ±5 mm to ±10 mm across the four jambs. The frame is bedded into the opening with the tape compressed unevenly until shims are adjusted. A target compression ratio of 40%–60% is common for this class of compressed foam tape. The actual ratio at any point is controlled by the gap between the frame and the rough opening. Old masonry and timber substrates contain dust, friable paint, and old sealant residue. These must be removed by brushing and vacuum extraction. The timber frame surface is checked for moisture content below 18%. Higher moisture reduces adhesive bond strength and promotes biological activity behind the tape. The adhesive face is pressed onto the frame jamb before the frame is set. The release liner is removed in a single continuous motion. The tape must not be stretched during liner removal. Stretching reduces recovery force and creates a thin section at the corner. The window is shimmed at load points to create consistent compression. Over-compression at the sill can block drainage. Under-compression at the head creates an air leak. The tape is integrated with a flexible flashing membrane at the sill and jamb flanges. Air barrier continuity is verified under ASTM E2112-19. The exterior joint remains vapour-permeable to allow outward drying. The internal vapour barrier is separate on the warm side. The tape must not bridge structural movement joints between dissimilar materials. Movement between timber and masonry may exceed the tape's allowable joint movement. In such locations, a back-up joint filler and an engineered sealant joint are used. The tape is not intended to serve as the sole water-resistive barrier. It is part of a redundant weather resistive barrier system. Fasteners are installed through the tape. The fastener holes must be predrilled through timber to prevent splitting. The final retrofitted window opening is an airtight assembly with a continuous internal air barrier and an externally drained perimeter seal. The interface between the tape and the rough opening substrate is inspected for gaps using a thin feeler gauge. Any gap larger than 1 mm is addressed with shimming or a supplementary sealant. The finished unit is then trimmed and painted at the reveal.

Compression Recovery After Temperature Shock in Modular Volumetric Wall Joints

Offsite modular wall panels arrive at the stacking yard with factory-fitted perimeter tapes. The tape is applied continuously along the exterior face of the module frame. During transport, the module is subjected to vibration, torsion, and crane-induced deflection. These forces cycle the tape before the building is weathertight. The tape must recover after each load event. At low temperatures, polyurethane foam stiffens. Recovery is delayed. At −20 °C, the tape may require 24–48 hours at +20 °C before full expansion. This delay must be considered in site assembly schedules. The joint gap between modules after stacking can vary from 5 mm to 15 mm. A 25 mm wide tape is often used in this joint class. It is compressed to 8–10 mm at mating surfaces. The 60–70% compression range provides a weathertight seal while allowing some panel rotation. The mating surfaces are cleaned of form-release oils and concrete dust. The adhesive face is pressed against the adjacent module using mechanical winches or hydraulic alignment jacks. The tape is not intended to accommodate structural shear between modules. The structural connection is made by corner castings and threaded rod. The tape only prevents air and water migration across the exterior joint. Its vapour permeability is important because interstitial moisture may otherwise accumulate between the module sheathing and the interior vapour barrier. Compression set is measured according to ISO 1856-2018. The test uses constant deflection under specified time and temperature conditions. The measured compression set quantifies the permanent thickness loss after stress relaxation. Low compression set indicates better recovery. Published data for Bostik T630 under ISO 1856 conditions is not always stated in open literature. Where absent, the installer must request the manufacturer’s declaration. A performance test under ASTM D3574-17 may also be used for slab urethane foams. The finished modular wall interface is protected by a vertical trim or external cover strip. The foam tape remains shielded from direct UV. The tape is not left exposed for more than 30 days of direct sunlight. UV exposure degrades the outer foam surface and reduces recovery force. A sacrificial weather shield is used during prolonged site storage. The terminal modular building assembly is then tested for whole-building air leakage. The tape contributes to the continuous air barrier only when the tape joint is continuous at floor and roof interfaces. Any interruption at the interface creates a leakage path. The perimeter tape is therefore continuously applied, not skip-applied.

When the Tape Must Function as a Vapour-Permeable Exterior Seal Behind a Rainscreen

Open-joint rainscreen assemblies separate the outer cladding from the supportive wall. The cavity pressure is partially equalized. The outer joint is intentional. Water drains and air moves behind the cladding. Bostik T630 AIRSEAL is applied to the window perimeter as part of the drainage plane. It must remain vapour-permeable to allow outward drying. The water vapour resistance factor depends on the cell structure and the compression state. Under high compression, the effective vapour permeance drops. Joint design must retain a minimum open-cell path. A continuous layer with 70% compression may act as a vapour barrier if the foam densifies beyond the open-cell squeeze point. This condition is tested per EN ISO 12572-2016 using the wet cup method. The measured water vapour transmission property of the installed tape is reported in the manufacturer’s declaration of performance. The open-joint rainscreen exposes the perimeter seal to intermittent wind-driven rain. The tape is not the primary rain-screen. It is the secondary drainage plane. The primary deflection is provided by the cladding. The tape joint is lapped at the horizontal sill and vertical jambs. The lower horizontal tape must be installed before the side tapes so that water is directed outward. A head flashing overlaps the top tape. The bond face must be protected from dust. Surface dust is removed with a brush or vacuum. The tape is installed before the cladding brackets are fixed. In a rainscreen cavity, the tape is often compressed between the window flange and the air barrier membrane. The membrane must be compatible with the adhesive. Some liquid-applied air barriers contain solvent residues that soften the adhesive. A peel test on the actual membrane is required. The terminal rainscreen assembly is drained and vented. The window opening remains weathertight while the cavity allows evaporation. The tape must not be installed where the exterior face is continuously wet. It is not intended for submerged conditions or below-grade use.

Aluminium window fabrication lines that use corner crimping or structural adhesive injection produce an irregular substrate at the diagonal joint. The tape is applied around the outer frame after the corner joint is cleaned and crimped. Residual adhesive squeeze-out must be removed before tape application. If adhesive is allowed to cure under the tape, it creates a hard ridge. The foam compresses unevenly around this ridge. The result is a local void at the edge of the ridge. A scraper or solvent wipe removes the squeeze-out. The cleaned corner is then primed if required. The tape is applied with a low-speed applicator to control tension. When the spool tension is too high, the tape stretches. Stretched tape has reduced recovery and may not meet the intended compression ratio. Batch-to-batch variation in adhesive coat weight requires lower application speed if peel values fall below the production control limit. The tape is cut at each corner with a butt joint. The liner is peeled back only after the frame is ready for glazing. The finished thermally broken aluminium window has continuous tape around all four sides. The terminal window is assembled with the tape protected from glazing sealant. Some glazing silicones contain acetic acid. Acetic acid may interfere with the adhesive if contact occurs before cure. The tape is masked during glazing. The finished window is installed into a prepared opening. The tape provides the surround seal between the frame and the rough opening. It is not a substitute for the internal glazing gasket. The frame is fixed with aluminium fasteners. The fasteners are installed through the tape. The tape must be pierced cleanly. A pre-punched hole in the tape reduces tearing. The installed window is checked for air and water leakage. The opening gap is controlled by shims. The final compression ratio is measured with a tape thickness gauge. The acceptable range is maintained on the production line by a template. This template is checked at each shift. The terminal product is a fixed or operable aluminium window unit with a consistent perimeter seal. The installation practice is recorded against ASTM E2112-19.

Door Threshold and Sill Interface Sealing Under Step-Edge Surface Water Runoff

A door threshold is subject to surface water runoff, foot traffic, and differential settlement. The tape is installed between the threshold and the rough opening sill. The threshold must slope outward at 1–2%. The tape is compressed under the threshold by the weight of the door and by mechanical fasteners. The outer edge of the tape is set back from the threshold edge to create a drainage drip. The joint between the threshold and the floor finish is sealed with a separate sealant. The tape is not used as the exposed walking surface seal. The adhesive must bond to the underside of the aluminium threshold. The underside is cleaned of cutting fluid and oxide dust. A mechanical abrasion of the anodised surface may increase bond strength. The tape is applied along the full length of the threshold. At the threshold ends, the tape must return up the jamb by at least 25 mm. This creates continuity with the frame jamb tape. The rough opening at the sill must be level within ±2 mm across the entire width. If the sill is not level, the threshold will rock and compress the tape unevenly. The door is then anchored through the threshold with stainless steel screws. The screws must not strip the substrate. The torque is limited by the threshold material and substrate. Over-torquing bows the threshold and opens a gap in the tape. The tape can be supplemented with a pre-compressed foam backer rod in gaps larger than 10 mm. The finished door threshold is load-bearing only at the screw and shim points. The tape is not a load-bearing element. It provides the air and water seal at the interface. Air leakage at the threshold is often the highest leakage point in a door assembly. The tape lowers this leakage by filling the irregular threshold-to-sill gap. The installed door is tested under ASTM E283-04 and ASTM E331-00. Water must not be drawn under the threshold by capillary action. The threshold design, the tape compression, and the outer sealant bead work together. The terminal product is a swinging or sliding door with a continuous perimeter seal and drained sill.